The radii of these ionic species follow the order (a) Ca^2+> K^+ > Cl^- >S^2-

Question

Consider the isoelectronic ions 

K⁺ ,S^2- ,Cl^- and Ca²⁺

The radii of these ionic species follow the order 

(a) Ca²⁺> K⁺ > Cl^- >S^2- 

(b) Cl^- > S^2- > K⁺ > Ca²⁺ 

(c) S^2- >Cl^-  >K⁺ >Ca²⁺ 

(d) K⁺ > Ca²⁺ > S^2- > Cl^- 

Answer 1

Correct option is (C) S^2- >Cl^-  >K⁺ >Ca²⁺ 

Isoelectronic species are those species which have same number of electrons. 

As all the given elements are isoelectronic with each other. 

Thus, the radii/size of isoelectronic species is inversely proportional to the atomic number, i.e. size \(\propto \frac{1}{Z}\)

Thus, the correct order is  S^2- >Cl^-  >K⁺ >Ca²⁺